Okay well a good example of what I mean are the Trojan wars - It is geneally agreed the Homeric epics began as an oral tradition of perhaps as much as four hundred years.
Now of course there is very good chance that emblishment occured and the story's point changed somewhat. However what didn't change was the core fact. Greece and Troy fought a war - Greece eventually won. Until the discovery of Troy, the whole story was always considered a myth.
I use the same arguement with Jesus, Buddha even Moses. The existence of the stories in the first place point to a high probability these people existed. Their deeds, actions and fate can be argued, because they are all elements that can be emblished or changed to suit the mood of the re-teller.
Where these people big bold and as imposing as the tradition might suggest. I think that is the subject of another thread altogether
And now fragments are coming out saying that Greece LOST the Trojan war.
Oral tradition is the most unreliable form of history you can have. Unfortunately, it's also, until recently, the most common, say the last 500 years or so.
you have to understand that Siddarta was a Indian prince. His life is documented elsewhere. That he existed is not in question. That he sat under a banyan tree and ate only lentils until he achieved enlightenment is under scrutiny. Moses is another story. IIRC, there's a good argument to be made that he's fictional, starting with there not actually being a record of a time when the Hebrews were enslaved, enmasse, by the Egyptians, but I digress, shamelessly.
Jesus is a different story altogether. ID does bring up some good points. There isn't a whole lot written about him, especially in the formative period after his death. There's almost nothing about his childhood (except for the one gospel, Gospel of Mary, I think?) is written about, none that is written is accepted as, um...gospel.
This being said, there isn't a really good argument to suppose that he didn't live. First, the time period that he was to have lived in is as well known as any of the same time frame. Second, the predominant culture that he was subject to was known to have been in the area. Third, some of those who came after him are accepted as having had lived (e.g. Paul). Fourth, his place in society would naturally exempt him from the normal documentary processes of his day. And so on. It all adds up to him being a difficult person to actually pin down. I understand those that say he didn't live, I used to be one, ask JJ. When I first got here, he and I locked horns over this very topic.
In the long run, it probably doesn't matter except to the most fundamental wings of both the Christians and atheist camps. The rest of us can accept the myth for what it is. Much like I accept the Poetic Eddas and Greco-Roman mythology for what they are, nice stories that our ancient forefathers used to try to help explain the world about them, give guidance as to how to get along. Were they perfect? Hell, no. The NT is rife with racism, misogyny, bigotry and general nastiness. There's some good bits too, though. It's an important set of books, even if it's not a good book. Western civilization is based heavily on the Bible, in general, and the New Testament in particular. No argument about Jesus having had lived or not will change that.
That's not to say that it should STAY that influential, just that it was that influential.